And then there was one. Of the three brave Pakistani politicians who stood up for Aasia Bibi, an embattled Christian woman flung on to death row last year, just one is still alive: Sherry Rehman. The liberal parliamentarian from Karachi, known for her glamorous style and outspoken views, spearheaded efforts to reform the much-abused blasphemy law after Bibi, a mother of four, was sentenced to death for allegedly insulting the prophet Muhammad.

Rehman, 50, was joined in her lonely struggle by two men – the Punjab governor, Salmaan Taseer, and the minorities minister, Shahbaz Bhatti. Now both of them are dead and worries are growing that Rehman is next. "Make no mistake: she is in grave danger, like nobody else," one friend said.

Rehman, is currently in New Delhi, visiting the Indian capital for a conference, in a rare public appearance. Since Taseer was gunned down by his guard outside an Islamabad cafe on 4 January she has lived in near hiding. She spent most of January holed up inside her Karachi home, surrounded by police and advised by senior government ministers to flee Pakistan lest she be assassinated.

"I get two types of advice about leaving," she said then. "One from concerned friends, the other from those who want me out so I'll stop making trouble. But I'm going nowhere."

In February she flew to Bangkok for a meeting on Pakistan-India relations; then more recently to the Indian capital. But at home in Pakistan she is largely absent from public life.

She flies to Islamabad discreetly, but rarely appears in parliament. Her movements have become secret, highlighting how a vibrant voice has been silenced by intolerant forces some warn could entirely suffocate Pakistan's fragile democracy. "We are the knife's edge. A clerical tsunami is headed towards us," liberal academic Pervez Hoodbhoy told a literature festival in Karachi last month.

Ironically, although many people have died as a result of blasphemy since the military dictator General Zia ul Haq made it a capital offence in the 1980s, none have been hanged under the law itself.

Instead dozens of blasphemy suspects, the majority of them Muslims, have been murdered, either while standing trial, in prison or after returning home. It's not just them – judges are fearful of ruling in blasphemy cases, fearing they too will be targeted.

In 1997, militants in Lahore gunned down a high court judge in his chambers as reprisal for having acquitted a Christian man on blasphemy charges three years earlier.

Now is the turn of the politicians, who are running for cover. Since the Bibi furore erupted, the ruling Pakistan Peoples party has strenuously avoided the issue, politically abandoning politicians who dare support reform.

Taseer, who found himself isolated in the last weeks of his life, has not been accorded the normal honours in the country's parliament; even allies who privately support his stand remain silent in public.

Critics say Rehman was rash in proposing legal reforms, that she attacked a sensitive issue too bluntly. "There's never a right time," she retorted in January. "Blasphemy cases are continually popping up, more horror stories from the ground. How do you ignore them?"

Now, friends say, Rehman is likely to face a deluge of fresh advice to shun the limelight. Less clear is how long she can remain out of sight. As history has shown, and Wednesday's events underline, Pakistan's flourishing forces of extremism can wait as long as it takes.

• This article was amended on 3 March 2011 to clarify details of Rehman's visits to parliament